Air flow control for flare stack

ABSTRACT

An apparatus for limiting air flow into a flare stack comprising an inlet tube closed on the upper end and terminating in an open lower end connected to the flare stack, a cup-shaped member coaxially spaced within the tube having a substantially closed end spaced above the lower end of the tube and an open upper end and an exit conduit coaxially spaced within the cup member and having an open end extending near the closed end of the cup member, said conduit extending upwardly through the closed end of the tube.

United States Patent Cullinane, Jr.

[451 May 16, 1972 54] AIR FLOW CONTROL FOR FLARE 764,860 7/1904 Moork ..431/210 STACK 3,055,417 9/1962 Reed ..98/60 [72] Inventor: Claude E. Cullinane, Jr., Houston, Tex. Primary ExaminerWilliam E. Wayner [73] Assignee: John Zink Company, Tulsa, Okla, 57] ABSTRACT [22] Filed: 1969 An apparatus for limiting air flow into a flare stack comprising 211 App] 792,010 an inlet tube closed on the upper end and terminating in an open lower end connected to the flare stack, a cup-shaped member coaxially spaced within the tube having a substan- [52] US. Cl ..98/60, 431/202 tially closed end spaced above the lower end of the tube and [5 l] Int. Cl 1 ..F23l 17/02 an open upper end and an exit conduit coaxially spaced within [58] Field of Search ..98/122, 58, 60; 126/312; the cup member and having an open end extending near the 431/202, 346 closed end of the cup member, said conduit extending upwardly through the closed end of the tube. 56 R f ed 1 e erences Cit 1 Claim, 3 Drawing Figures UNITED STATES PATENTS 686,979 11/1901 Kloeb ..61/68 7 2/ B "T J 3 PKTENTEnnms m: 3.862.669

//vv/v TOR CLAUDE E CULLl/VA/VE, JR.

BY Q ..AA-L,

ATTORNEY AIR FLOW CONTROL FOR FLARE STACK This invention relates generally to apparatus for limiting the backward flow of air into a flare stack and more particularly to an improved device for installation near the exhaust end of a flare stack which limits the flow of air thereinto when an upward flow of gases lighter than air is interrupted.

Combustible gases such as hydrogen, hydrocarbons and the like produced in some industrial processes must sometimes be vented to the atmosphere or burned as waste gases. Such gases have a molecular weight less than that of air and will rise through a flare stack. Mixtures ofsuch gases with air are combustible and often explosive. It is therefore important to limit the presence of air in a flare stack to avoid detonations of gasair mixtures.

It is an object of the present invention to provide a device for limiting the flow of air into a flare stack and to provide a device which is of simple construction and effectively limits back flow of air into a flare stack when there is no upward flow of gas therethrough.

Another object of the invention is to provide an improve device which functions to limit entrance of substantial volumes of air into a flare stack through the exhaust end thereof by providing zones of different pressures.

Other objects and features of the invention will be appreciated and become apparent as the present disclosure proceeds and upon consideration of the annexed drawing taken with the following detailed description wherein an exemplary embodiment of the invention is disclosed.

In the drawing:

FIG. 1 is a side elevational view of an embodiment of the invention;

FIG. 2 is a longitudinal section view;

FIG. 3 is a cross-sectional view taken on the line 33 of FIG. 2.

The foregoing objects and others are attained in accordance with this invention by providing a device adapted to form a portion of a flare stack and consisting of a housing divided into a series of interconnected longitudinally extending annular passages through which gases rising in the stack flow upwardly then downwardly and again upwardly creating zones of different pressures in the housing to limit the volume of air flowing downwardly into the stack when an upward flow of gas is interrupted.

Referring to the drawing a housing is provided at its lower end with flange 12 for attachment to a tubular section 14 of a flare stack. A flange 15 carried by the upper end of the device is adapted to be welded or otherwise secured to a tubular element 16 forming the exhaust end of the flare stack. The housing 10 is of larger diameter than the tubular sections making up the flare stack. A pilot 17 may be positioned adjacent the exhaust end of the stack so as to direct a flame into the presence of the gas escaping through the open upper end of the stack.

A tube 18 extends downwardly through the conical portion 19 of the housing 10 as shown in FIG. 2. The tube 18 has an open lower end 21. A cup-shaped member 22 is disposed substantially concentrically about the tube 18, and has its open end 23 adjacent a zone A within the housing 10. A disc-shaped wall 24 closes the lower end of the member 22. A zone B is provided within the lower end of the cup-shaped member 22. An annular space 26 is formed between the perimeter of tube 18 and the internal surface of the cup-shaped member 22. The housing may be substantially concentric with the cup-shaped member 22 and spaced therefrom to form annular space 27 therebetween.

The cup-shaped member 22 is provided with a drain pipe 28 equipped with a goose-neck shaped trap 29 which permits liquid to drain from the device without loss of gas. The cupshaped member 22 may be supported by radially disposed arms 31 secured to the wall of the housing 10.

In operation, gas supplied into the base portion of flare stack rises upwardly through annular space 27 and then downwardly through the annular passage 26 and then upwardly through tube 18 and to the top of the stack. Ignition of the gas takes place adjacent the pilot 17.

When the gas entering the lower end of the housing 10 has a molecular weight less than that of air (less than 28.966) a zone A having the greatest pressure in the device will be created because of the buoyant energy of the gas. A lower pressure will exist throughout the zone B. Since gas will not flow from a zone of lower pressure to one of higher pressure, air entering the flare stack through tube 18 while there is no gas flow upwardly through the stack will not move from zone B to zone A. Air is therefore prevented from entering any substantial portion of the flare stack.

If the gas in zones A and B has a molecular weight greater than that of air, the greatest pressure will be at zone B and the least pressure will be at zone A. Under these conditions substantial volumes of air will not enter the stack and the lower pressure is atmospheric and the greater pressure is above atmospheric. These differential pressures are created by the relative densities of the gases in relation to density of air at Fahrenheit. The gas is either lighter or heavier than air depending upon the relative molecular weights at a given temperature.

The cup-shaped member 22 is provided with a drain for liquids to prevent an accumulation thereof in member 22. Such liquids may develop from condensation or from rain or snow entering the open end of the stack.

The relative volumes of annular spaces 26 and 27 and the diameter of the stack are proportioned in order to accommodate the required gas flow and to create the required zones of differential pressures. While the invention has been described in detail for the purposes of illustration, it is to be understood that variations can be made without departing from the scope or spirit thereof.

What is claimed and desired to be secured by Letters Patent 1. Apparatus for limiting the flow of air into a flare stack having an upper exhaust end and a base adapted to receive a gas comprising, a tube extending downwardly from the exhaust end and terminating in an open lower end, a cup-shaped member having a substantially closed end spaced below the open lower end of said tube, said cup-shaped member having an upper open end and an annular wall surrounding the tube in spaced relationship providing a first annular space between the exterior of the tube and the interior of the annular wall through which the gas may flow downwardly, a housing surrounding said annular wall in spaced relationship providing a second annular space between the wall of the housing and the exterior of the annular wall through which said gas may flow upwardly, means for closing said housing about said tube above said upper open end providing space for gas flow from one annular space to the other, means for joining said housing to the base portion of the flare stack in a position to receive gas therefrom, and means for draining liquid from the cupshaped member. 

1. Apparatus for limiting the flow of air into a flare stack having an upper exhaust end and a base adapted to receive a gas comprising, a tube extending downwardly from the exhaust end and terminating in an open lower end, a cup-shaped member having a substantially closed end spaced below the open lower end of said tube, said cup-shaped member having an upper open end and an annular wall surrounding the tube in spaced relationship providing a first annular space between the exterior of the tube and the interior of the annular wall through which the gas may flow downwardly, a housing surrounding said annular wall in spaced relationship providing a second annular space between the wall of the housing and the exterior of the annular wall through which said gas may flow upwardly, means for closing said housing about said tube above said upper open end providing space for gas flow from one annular space to the other, means for joining said housing to the base portion of the flare stack in a position to receive gas therefrom, and means for draining liquid from the cup-shaped member. 